Last couple of races, on the way home, my stomach just gets achy. It feels like I have bad gas or a bug or something. It's really very painful and doubles me over in pain. Yesterday for example, I raced with water only and no gels. Usually I use cytomax and gu or something so I thought that might be the cause but it doesn't seem to matter.
Your help is always appreciated.

Your most recent stomach cramps are likely due to low serum sodium, potassium and chloride levels as you did not take any electrolyte containing sport drinks or gels during your race. You continually loose sodium, potassium and chloride in your sweat and unlike calcium (which you also loose in your sweat) you do not have a massive store of these other electorlytes that your body can draw on to keep your blood levels normal.

Now with the stomach cramping you were experiencing with your other rides, taking too much carbohydrate in the form of energy gels and/or too concentrated a sport drink, can cause stomach cramping as well.

What you will need to do is find a happy mid point. Mix your sport drinks to 1/2 to 3/4 strength and drink plenty during your work out. Shoot for 1-2 quarts per hour of work out or racing. With high heat and humidity days you should be hitting the 2 quarts an hour mark and running closer to 1/2 strength. With days of lesser heat and humidity you can target for the 1 quart an hour mark and mix your sport drink at 3/4 to full strength. Experiment on your training days and stick to what works on race day.

You also should eat a meal that is easy to digest, provides complex carbohydrates and protein no sooner than 2 hours before your race or intense workout. This will help decrease cramping in your gut from blood being redirected from your muscles and away from your gut.

Another possible factor is swallowing air while gulping down fluid during the intensity of the race. Try a CamelBak system if you are not already. My experience with these is the large flow valve allows easier drinking with less airswallowing from drawing hard.